Sortilin is the major 110-kDa protein in GLUT4 vesicles from adipocytes.
Vesicles containing the glucose transporter GLUT4 from rat adipocytes contain a major protein of 110 kDa. We have isolated this protein, obtained the sequences of peptides, and cloned a large portion of its cDNA. This revealed that the protein is sortilin, a novel membrane protein that was cloned in another context from a human source while this work was in progress. Subcellular fractionation of rat and 3T3-L1 adipocytes, together with GLUT4 vesicle isolation, showed that sortilin was primarily located in the low density microsomes in vesicles containing GLUT4. Insulin caused a 1.7-fold increase in the amount of sortilin at the plasma membranes of 3T3-L1 adipocytes, as assessed by cell surface biotinylation. The expression of sortilin in 3T3-L1 cells occurred only upon differentiation. Previous characterization of sortilin has led to the suggestion that it functions to sort lumenal proteins from the trans Golgi. The significance of its insulin-stimulated increase at the cell surface and of its expression upon differentiation will require definitive delineation of its function.
Morris
N J
NJ
Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
Ross
S A
SA
Lane
W S
WS
Moestrup
S K
SK
Petersen
C M
CM
Keller
S R
SR
Lienhard
G E
GE
D016475:3T3 Cells; D033942:Adaptor Proteins, Vesicular Transport; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001692:Biological Transport; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D018076:DNA, Complementary; D051275:Glucose Transporter Type 4; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009124:Muscle Proteins; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D000099183:Sortilin
D033942:Adaptor Proteins, Vesicular Transport; D018076:DNA, Complementary; D051275:Glucose Transporter Type 4; D008562:Membrane Glycoproteins; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D009419:Nerve Tissue Proteins; D011994:Recombinant Proteins; D000099183:Sortilin; C495693:Slc2a4 protein, mouse; C495694:Slc2a4 protein, rat